WO 98/47880 and JP-A-2000-186077 disclose that 3-[(1S)-1-(2-fluorobiphenyl-4-yl)ethyl]-5-{[amino(morpholin-4-yl)methylene]amino}isoxazole represented by the following formula 1 is useful as, for example, an excellent therapeutic agent for autoimmune diseases, inflammatory diseases and the like:

However, although these references disclose the isoxazole derivative of the formula 1, they do not disclose crystalline isoxazole derivative of the formula 1 which is easy to handle and stable in a process of its formulation into a pharmaceutical preparation and a pharmaceutical preparation containing this derivative.
Iyakushin (Pharmaceutical Council) No. 64 (issued on Feb. 14, 2000) supplies “guidelines for a bioequivalence test on oral solid pharmaceutical preparations different in the content of an active ingredient”, and it has become necessary that oral solid pharmaceutical preparations different in the content of an active ingredient should exhibit equivalent release-by-dissolution behaviors in each of test solutions (e.g. buffer solutions or water) having pH values of 1.2, 3.0 to 5.0 and 6.8, respectively, corresponding to the pH values in digestive tracts. Pharmaceutical preparations having good release-by-dissolution properties are relatively easy to obtain as pharmaceutical preparations that exhibit equivalent release-by-dissolution behaviors irrespective of their different active ingredient contents, but the production of a pharmaceutical preparation of a difficultly water-soluble compound such as the isoxazole derivative of the formula 1 is generally difficult because the compound has a low affinity for water.